This invention relates to disk drive systems equipped with a programmed microprocessing assembly or like autonomous control device capable of responding to stimuli external of the disk drive and to conditions within the disk drive in order to perform independent rational functions. In particular, the invention relates to self-testing of disk drive systems.
It is a general practice to test disk drives through external stimulus, as through a central controller of a host computer system under operating conditions which include carriage motion. Recently autonomous controllers within disk drives have been developed. Such disk drives have control and decision making capability sufficient to carry out preselected rational functions either interactively with the host control device or independently of the control device. For example the ISS/Sperry Univac Models 7350 and 8450 Disk Drives, manufactured by ISS/Sperry Univac of Cupertino, Calif. now incorporate microprocessor assemblies which have been preprogrammed to perform most of the traditional functions of random logic within disk drives.
Heretofore extensive fault diagnosis of disk drive internal workings has not been known, although some fault diagnosis has been carried out through host controller systems. The fault diagnosis of host controller systems has typically involved exercising the disk drive system components under operating conditions, as for example by moving the carriage which supports the read and write heads confronting the rotatable magnetic disks. A malfunction is detected by the failure of the disk drive to correctly transfer address or data information signals to the host controller via an interface input/output (I/O) bus or to a resident memory associated with a host central processing unit via a read/write (R/W) data bus. When a malfunction or fault is finally detected as a failure, there may have already occurred internal damage to the disk drive or loss of data. A typical failure is for example a "head crash" caused by malfunction in the carriage servo circuitry causing data to be lost or the magnetic surface of the disk to be damaged. Heretofore it has not been known to detect failure in servo circuitry unless the carriage is moved.